How is stainless steel classified according to its crystal structure?

How is stainless steel classified based on its crystal structure?
Stainless steel is an alloy steel composed primarily of iron with other alloying elements. Its core characteristic is the formation of a dense chromium oxide passivation film, which prevents further corrosion of the metal within, resulting in excellent corrosion resistance.
Stainless steel can be classified in many ways, but the most common classification is based on its crystal structure at room temperature, which is divided into three categories:
1. Austenitic stainless steel:
Austenitic stainless steel has a face-centered cubic structure and may become weakly magnetic after cold working. It contains 16%-26% chromium (Cr) and 6%-22% nickel (Ni). Nickel is a key factor in stabilizing austenite. Austenitic stainless steel exhibits excellent corrosion resistance, plasticity, toughness, and ease of processing. It also exhibits excellent high-temperature resistance. Typical grades include 304 austenitic stainless steel, 316 austenitic stainless steel, and 309S/310S austenitic stainless steel.
2. Ferritic Stainless Steel:
Ferritic stainless steel has a body-centered cubic structure and is magnetic. It contains 10.5% to 30% chromium (Cr). It offers moderate corrosion resistance, good oxidation resistance, and a low cost. Typical grades include 430, 409, and 446.
3. Martensitic Stainless Steel:
Martensitic stainless steel has a body-centered tetragonal crystal structure after quenching and is magnetic. It contains 11% to 18% chromium (Cr) and a high carbon content. Martensitic stainless steel offers high strength, hardness, and wear resistance. Common grades include 410, 420, and 440C.
Other specialized stainless steels include duplex stainless steel and precipitation-hardening stainless steel.